RE: Reducing impact of save/restore/dump on Dom0

["Graham, Simon" <Simon.Graham@stratus.com>]

> On linux, there is another way beside O_DIRECT: it's possible to
reduce
> the memory used for cached writing using the sysctl vm.dirty_ratio;
> I've
> used this to reduce the impact of heavy cached writes on dom0 with
good
> results.
> 
> Maybe it helps for save/dump also...

Oh interesting -- I shall look into this. 

I just took a quick peek and it is set to 40% in Dom0; I do see free
memory go to zero during a dump (and save/restore) plus I see the
waitIO% go to near 100% and Dom0 becomes somewhat unresponsive;
specifically what we see is that domain boot fails during this time
because of a XenBus timeout waiting for the hotplug scripts to finish
adding the VBD in Dom0.

I still feel that dump/save/restore files really don't belong in the
system cache at all since they just pollute the cache for no ggood
reason.

Thanks,
Simon